Review: Meng Yayi KT88 Monoblocks

Meng Yayi Mini KT88 Monoblocks review (quite long)

It’s easy to find reviews of expensive amps but rarely do we find reviews of (extremely) affordable ones. Let alone from direct-to-consumer, over the internet, Chinese made amps. So I thought I would indulge here with a review of the Meng Yayi KT88 monoblocks. I have come across many audiophiles in chat groups asking about them, but no one to actually answer. At about $650 for a pair, including shipping no less, they are a rare steal. The question everyone asks is “can a cheap Chinese amp be any good?”. Well, I ordered 5 of these monoblocks (yes, 5) and played with them for about a year and a half now. I used them in many applications: as the centerpiece of my main stereo system for music listening; in a full 5.1 Home Theater set-up (hence the 5 monoblocks); and also as a 10 hour/day work office set-up. In the process I experienced break downs and set backs; but let’s start at the beginning.

Ordering the amps was easy – they are available on ebay and through a few other websites, including on9mart.com where, 18 months ago, I ordered a first set of two. I had a few questions ahead of ordering and they were quick and responsive – if in broken english, which is no problem. Within a few days I received an email with plenty of pictures of the amps being packaged and the labels taped on the boxes, including close-ups of the labels with tracking numbers. I was impressed. I have never seen such thoughtfulness from any manufacturers in my life. Sure enough, the tracking registered right away and 6 days later the amps were delivered by DHL to my place, in perfect condition.

Inside the boxes were the amps, fairly well protected (no damage), plus all the tubes in small nondescript white boxes with bubble wrap. Obviously no brand name tubes here, but all was fine. I can’t say that I was impressed with the workmanship of the amp though – but I wasn’t expecting otherwise, not at this price anyway. The wood trim is held in place with glue (the hot glue kind), with beading squeezing out at the extremities probably while the piece was pushed in place. A quick work with the Xacto knife cleaned this up easily enough. The printing on the amps looks amateurish, but once again, what did I expect? The amps are heavy (no lightweight transformers in there) with no loose parts, which is what counts at this point. Like I said the tubes are truly generic, with inconsistencies that are worrisome on the surface: for example the 6J4P tubes are quite different on both amps. Although they are from the same manufacturer (from the graphics and codes), they are obviously different – one is taller than the other and the bases are of different silver hues. Would this influence the sound? I wondered.

All the tubes went easily in place and the sockets were straight (I hate having an amp where tubes are slanting like the Pisa tower – these were all standing tall and straight).

I plugged the amps in my stereo system, feeding from a vintage Marantz tube preamp to a pair of Acoustic Zen Adagio speakers. The Meng Yayi monoblocks have two gold plated (is it really gold?) input ports, labeled “CD” & “AUX”. The CD input turns the monoblocks into an integrated amp of sort, which means that the volume is controlled by the pots at the front. I say “integrated amp of sort” because it is beyond me why one would use monoblocks in that fashion. Controlling the volume that way means turning the pots from each monoblocks in perfect unison to keep the balance from left to right. On the other hand using the “AUX” input bypasses the volume pot and turns these amps into true mono amplifiers. It is a good thing as the pots are of very dubious quality: they do not feel smooth or nice at all to turn. Better to bypass them, have a simpler signal path, and be done with it.

The Mini Yayi KT88 monoblocks are the most powerful tube amps that I personally owned so far; and at a rating of 50 watts each they are much more than my Acoustic Zen speakers require to shake the house. During all my listening I never really cranked the volume much more than half. But what I was happy about was that right at the onset the sound was miles ahead of any solid state amps I ever used with the Adagios. It is no secret that Acoustic Zen speakers react well to tubes (Robert Lee from Acoustic Zen will say so himself), and my experience supports it wholeheartedly. Where the speakers were previously lackluster, suddenly the level of depth bloomed in the music. I was expecting this as my small 8 watt integrated (6L6 tubes) is driving the speakers to a similar effect, albeit with a lack of power.

I made a conscious decision to give the Meng Yayi KT88 monoblocks some serious hours of play time before starting to truly listen to them – as from the onset there was a possible cloud over the horizon. There was a hum generated in the speakers, at the same frequency as the hum emanating from the transformers in the amps. To hear the hum from the amps I had to keep my ear close by – at about10-12 inches or so. The hum in the speaker drivers could be heard from about 2-3 feet away. It’s not much, but enough to be worrisome. Of course it was unnoticeable when any kind of music was playing, but knowing it was not the best feeling. A letter to the company yielded 2 things: a suggestion to buy a power conditioner for the electrical input; and to wait until the units had some more burn-in time to settle things down. I quickly decided against buying a new power conditioner as I never had such a problem in the past – it didn’t make much sense that this may be the problem this time around. But I decided to wait as it is a fact that some vacuum tubes are noisy when new until they settle down. So any serious listening test was put on hold.

Alas, a more serious hiccup happened. About 2 weeks after having the amps one of them ceased to work. It would power up but no signal would come out. This is where all the warnings one can hear over the internet came back rushing: buying overseas makes repairs a real pain in the cheeks. Sending the Meng Yayi back would have costed me a fair amount of money, plus the waiting time involved. Instead I decided to bring the faulty unit to a local tube amp repair shop in San Francisco. A few days later I picked up the amp, paid the $95 for the repair (a few resistors failed, they said, and replaced them with better ones), and brought it home. As soon as I plugged it a loud *pow* signaled an explosion and thick black smoke came out billowing from the side vents. Great. I turned it off right away and took it right back to the repair shop, dreading that this was the real end of the unit. So maybe they said that they repaired with better parts, but I learned a lesson about the better workmanship in America over China: it means little. The repair was worse than the original workmanship. At any rate another week passed and I got the amp back. They would not say what went wrong, and there was no fee for the second repair. This time the amp worked fine.

One would say that I would have learned better, but I was wondering still: could this just have been a fluke? I wrote to Meng Yayi again and told them the story, and also told them I wanted 3 more units (my goal was to try this in a home theater system). They apologized for my bad experience and said they’d send some nice interconnects for free with the shipment of the new amps. The same shipping process as above happened (and still impressed me) and a week later I had 3 more Meng Yayi KT88 monoblocks. But no interconnects. Further efforts proved futile: I would never received the interconnects. One can see here the limit of customer service with an oversea supplier. There isn’t much leverage. But in the meanwhile I was starting to play with 5 monoblocks.

Right of the bat, one didn’t work. A few minutes of detective work pointed out towards the blown power fuse. The Meng Yayis come with spare ones, so all it took is a minute to change it. No problem. One of the amp had something strange though: the AUX input and CD input were reversed. Although I was flummoxed at first, once I discovered the problem it proved to be an easy fix as well – all I had to do was to switched the cables to the other input sockets. Nevertheless there’s a real cautionary tale here: if the installation/soldering of such parts can be overlooked at the manufacture, what does it say of the rest of the circuit and how it’s built? While I didn’t find any other problem from there on, it makes one wonder – and can be a hit or miss like I experienced.

Score so far on 5 amps: 1 major break down, 1 serious mishaps (reversed input ports) and 1 minor problem (fuse). I need to admit, not exactly stellar. But what about the sound – isn’t it what it’s all about?

I used two monoblocks in my stereo system for about a month and listened to music every day. The hum subsided slightly, but not completely. These are not what I would call “dead quiet amps”. In all honesty, though, I love the sound. Three dimensional is the adjective that comes to mind. The voices are particularly luscious and float apart from the music. The impression of dimension, or volume in space, is intoxicating. So much so that I wanted more. The highs were at first slightly bright but subsided quickly to a great balance after a couple of weeks of listening. The bass is adequately deep and rich but very far from boomy – in fact I know that the Adagio speakers are capable of much more oompf in the low end than what the amps were driving. The Sigur Ros Hvarf Heim album is quite a test: the piano solo at the beginning is absolutely breathtaking, but when the bass starts billowing the sound gets compacted and starts losing punch. Could it be better? Of course, it isn’t hard to imagine. Did I enjoy the music anyway? Absolutely.

Next I installed all 5 amps in a home theater set-up (the lone unit for the center channel). I will not bother you too much with the details, as ultimately the experience was a fiasco. Multiple factors contributed to the disbanding, but the 2 major culprits were the aforementioned hum and the hopelessness of the A/V processor I used. The hum first: on a two channel system, listening to music from 8 feet away it is not much of an issue. For a HT system with 5 speakers humming, some near your ears, it becomes an issue. During some dead quiet moments in a movie one can concentrate on the speakers and hear it. I am not sure if any of my guests ever noticed it, but I knew it was there and it was enough. The second problem is irrelevant to the amps but contributed just as much (if not more) in stopping the experiment: the A/V processor, an Emotiva UMC-1, was a hopeless piece of electronics that went back to the manufacturer 4 times for repair (the 4th times it was replaced with another, used, unit) – all to no avail. I ended up getting rid of it, which ended the experiment of using the Meng Yayi KT-88 as HT monoblock amplifiers. Of note: even with all the monoblocks turned off (or even disconnected), the Emotiva unit transmitted as a direct line its own hum to the speakers! I have no doubt that this contribution made the whole setup a fiasco. Here’s what I learned: Emotiva may be an American company, but when it came to repair its own unit the experience was as hopeless as the idea of sending a monoblock back to China for repair.

After that I took 2 monoblocks to work where they replaced an aging Fatman iTube. I connected them to two Wharfedale Evo2-10, and drove the music from the iMac computer. Right away the increased power over the 13 watts of the Fatman made itself felt. The music became instantly more vibrant and luscious. An interesting side effect happened: while the sound on the Adagios has a crispy clear high range, extremely dynamic and detailed – the bottom end always feels lacking. But on the Evo2-10 it is never the case. The bass is well driven and very clear – even deep – but the highs are more muddled. Obviously I already know that the Wharfedale speakers have a wonderful mid-range sound that I like (it is why I chose them for my work place, as I listen to them nearly 10 hours a day and the sound is never fatiguing). The tweeters are not as efficient as the ribbon tweeters on the Adagios, so that explains that. But why the increased bass befuddled me: where did it come from? After all the Evo2-10 are smallish monitor speakers and surely can’t match the Acoustic Zen deep bass reflex. It struck me that the only differences are in the sensitivity of the speaker drivers and the noise level of the environment. My house is eerily quiet at night while my office has a constant noise level from anything and everything. As such the two Yayi monoblocks in my office are nearly always driven between 35% to 60% of maximum power; while the house monoblocks rarely go over 20%.

So I tried something: I stayed late at work one night, waited until the world went quiet, then lowered the volume to a power level closer to my home average. Ah-ha! Somewhere around 25% and below the bass suddenly begins fading away and losing its punch. The bass started feeling flat and anemic: but all is relative – it was still much better than what the poor Fatman iTube was previously doing. I did the reverse experiment at home, which was somewhat painful to my ears: I increased the volume and kept an eye to the bass. Sure enough the depth of the bass and its definition increased as the volume climbed. Except that I would never want to listen to music at that level.

It seems that the built configuration of the Meng Yayi KT88 monoblocks asks for them to be run hard in order to deliver the full range without an unwanted drop in the bass frequencies. I am now considering adding a subwoofer to the stereo system in order to shore up the bass at lower volume.

I ran into a great write up the other night (on 6moonsaudio) about tube rolling, and the sonic difference between tubes. Here’s an excerpt from the article (found at http://www.6moons.com/audioreviews/tj+synergy/1.html – excerpt is pulled from page 2):
“Sonically the classics (vacuum tubes) are more fluid, midrange-centric, burnished and opulent as well as bandwidth-limited and dynamically less potent. The moderns have wider bandwidth and stronger bass. They sound more linear and controlled/damped. In trade they give up some ne sais quoi of the classics. It would be astute to say that for classical music, the classic tubes are more compelling for their greater succulence and fleshiness in the timbre domain. For hard-hitting bass-potent modern fare, the tauter more robust and dynamically stouter but also drier moderns would seem more appropriate. Needless to say, none of this factors listener preference. Nor does it the very real influence of driver tubes which often exert more control over the final sound than the designer output glass.”

What it may possibly mean is that the Meng Yayi monoblocks could possibly live up to a fuller potential with sonically better tubes. Maybe there’s more to discover yet with different tubes than the very cheap original ones – maybe to the point of correcting some if not most of the lacking.

Now back to the hum. Guess what, it (nearly) completely disappeared from the units at work. They have been playing for nearly six months now, 8 to 10 hours a day. I didn’t notice at which point the hum subsided but the amps have well over 1000 hours of play in them. The amps at home still have a slight hum, but they have maybe 300 hours of play so far. That and the fact that the Acoustic Zen speakers are much more revealing of such flaws.

Ah – a last detail: one of the blue LED that lights the middle vacuum tube (for mood only) burned off in one of the amps at work. Once again, no big deal but it does bring the whole quality issue at the forefront once again.

In a nutshell, the verdict: the sound is warm and luscious. The midrange is very forward, clear, well defined and never sharp. It’s a “big” sound in the classical sense and very dimensional, human and perfect for vocal; but much less so for hard rock or metal. This is what this amp is good at: the midrange warmth and touch. The bass is lacking unless you like to crank up the volume; the highs require a fast ribbon tweeter in your speakers to make them soar. I like to think of these monoblocks as delivering a sound shaped like a bell curve: all the power and detailing is in the middle, the more it strays form it the flatter it gets. Cranking up the volume adds power to the ends and somehow flattens the curve, giving you more bass details and treble dynamic. Would I buy these amps again? Honestly, probably not – not with the number of problems I had with them. Yet I will keep them longer and start rolling tubes. That whole world remains to be explored.

As a more generic question, would I buy another Chinese amp again, knowing what I now know? Most probably yes. Truth is, the Meng Yayis are incredibly cheap for monoblocks with KT88 tubes, so I couldn’t expect too much to start with – and yet the sound itself isn’t half-ass bad. In fact it is quite soothing. Could a slightly more expensive, better built amp bridge up the shortcomings of the Meng Yayi KT88 monoblocks? I would like to think so. Let’s be honest here, a huge number of better known western brands have their amps built in China. They are perfectly fine and trusted upon. They are not better because they are more expensive – the are more expensive because the brand name is added on top, along with the distribution network and retailer profit. They are better because there is a known quality control happening, and hopefully a well designed circuit. But they are still made in China. In other words better amps can be found (and are made) in China. The Meng yayi may not be the panacea, or even the best example, but I believe that somewhere there’s the right source waiting to send me a great amp – not just an okay one. Which brings me to…:

Big surprise, I am now toying with the idea of getting another tube amp from, where else, China. I’d like to replace the Fatman that has now moved in my bedroom (driving two Wharfedale Diamond 10.7). That would be another fun experiment to do! I’m wondering where my searches will take me…

Serge McKig
Berkeley, California

username Sergemckig